Miniaturization and larger capacity are demanded according to the miniaturization of electronic and electrical equipment in capacitors and an improvement in insulating characteristics is simultaneously demanded according to the higher voltage the capacitors are used. In response to the demands, in film capacitors, studies have been made on thinner films as a dielectric and on a reduction in pinholes present in films. The electrostatic capacity based on unit volume of the film as the dielectric is in inverse proportion to the square of the film thickness and in proportion to the permittivity of the dielectric. Although the miniaturization and larger capacity of capacitors can be achieved in film capacitors by forming thinner films which are dielectrics, operating efficiency is lowered in processing steps of capacitors, and especially the operating efficiency is lowered in steps of metal vapor deposition on films and slit processing and winding for stacking a film of a piece of capacitor. A proposal was made for a method for suppressing the deterioration in operating efficiency by adding specific inert fine particles as a lubricant into a polyethylene-2,6-naphthalenedicarboxylate film [JP-A (JP-A refers to Japanese Unexamined Patent Publication) No. 10-294237].